Treatment of hydrocarbon oils



Feb, 8, 1944. W, Rupp ET AL 2,341,389

TREATMENT HYDROCARBON OILS X Filed Nov. 9, 1940 o o o QN wm Q u ww mw ww d F F mw Mw ai \v\. \v\. In. QN Nuuvvwwhw $400.0 \M mi Q M w Flu. 9 M., T MQNJ h www MN h a "i, F INH HH NN HH w mm A s, 9, w Nm. HHH\.%N. l Ouh NBQL Wauw $9 Q 9N L BBM-Mi? Patented Feb. 8, 1944 UNITED STATESA PATENT OFFICE` Waiter n. Rupp, mountainside, and -rrea c A Hanker, Jr., MapleWood,N.J., assignors Ato Standard Oil Development Company, ra corporation of Delaware Application November 9, 194),SerialNo. 3'64g950 Claims.

'This invention relates to certain improvements in the treatment of hydrocarbon oils and is more particularly concerned with the desulding, stabilization and fractionation of hydrocarbon distillates such as naphthas, heavy naphthas, gas oils and the like.

Naphthas obtained for example in pressure cracking operations -frequently contain relatively large quantitiesof hydrogen sulfide. in addition, they usually contain small amounts of light hydrocarbons such as propane, butane and pentane which are too volatile for the purposes for which the naphtha is to be used. These undesirable constituents must be removed before the naphtha is fit for commercial use. The naphtha fraction must also `frequently be fractionated in order to obtain oils of the proper boiling ranges -for particular purposes. These and other objects are accomplished by Astabilization and fractionation or rerunning. Heretofore stabilization has been carried out in a tower operating on the depropanizer principle in which the naphtha to be treated is introduced into a tower the top of which is maintainedata relatively low tempera- 'tureand the bottom at a relatively much higher temperature. The undesired lighter fractions and hydrogen sulfide are removed'from the top 'of the tower and the desulfided and stabilized naphtha removed from the bottom of the tower.' These bottoms'are still at a relatively high temperature and they are ordinarily cooled by means of water in a shell and tube type cooler. The removal of heat in this manner is not only a lwaste of heat but involves'additional investment and operating expense which makes the entire operation unduly costly. 'Subsequently the cooled stabilizednaphtha may have to be rerun and this operation involves reheating fof the naphthas to a suitablererunning temperature.

It is a particular object ofthe present invention to provide a new and less costly method of desuli'lding, stabilizing and rerunning hydrocarbon distillates in which the heat content of the stabilized naphtha is utilized instead of being ventionfis not limitedto such 'a distillate but .is equally applicable to other types of `hydrocarbon distillates which must fbestablized .and rerun.

A Referring to fthe drawing, numeral 4i designates a supply itank of craokedinaphtha` to be treated. Pump 2 iwithdrawsrnaphtha fromtank i 'through Iline 3 `and forces it at atmospheric temperature through line 4 into the utop portion of a conventional type plate tower 5 operating on `the depropanizer principle. The bottom of the tower is maintained `at a vtemperature eof say 1250 to '300 F. .by -continuously withdrawing .liquid through line '6 by means of pump 1 and forcing it through 'line 8 `into and lthrough an indirect heating means `irland then 'returning it into the tower throughv 'line it at 1a point somewhat above the bottom thereof. The heating means 9 may be supplied with 'any convenient heating mediumusuch for example as steam. The tower 5 fis maintained under pressure, preferably of about'O iso-100 pounds per squareinch. With the lheat supplied to the bottom of the tower sufficient to maintain a temperature between A25()I -and rOO" F. the top of the tower` will 'be maintained at ra temperature between =l00 and '130 F.

Gases .and vapors are removedA from the ltop of tower '5 through line ll, are passedk through a cooling means IZ-and then discharged through Aline i3 into a separator 'I4 from which uncondense'd gases are removed through line `i51and `condensate through line i6. It lwill be found `that substantially all of Athe hydrogen sulfide content of the original naphtha will be removed through line I 5. The condensate may be passed to the main refinery stabilizing system or otherwise disposed of.

A portion of the bottoms vleaving tower 5 through line i'iwill be required `to becirculated through the reboiler circuit to maintain tliebot- Itom `of the tower atthe desired temperature. The remaining portion of the hot bottoms v'from tower 5 will be vwithdrawn from line 8 through line i' and intrcducedinto a second .tower '.18

` in Vwhi'chfurther:stabilization and fractionation of the desulded naphtha -takes place. :Tower i8 may also be a conventional type yplate .tower essentially similar to tower J5. :Prior 'tofthe .in- -troduction of the .hot "bottoms :from ftower `introltower Tit, all or la: portion thereof .are passed through heat exchanger T29 wherein 'they 'are heatedV by -indirect heat exchange 'with the into tower I8 may be effected by passing all or a portion thereof through a heating coil. In the drawing the hot bottoms from tower are bypassed around heat exchanger I9 and passed into 20 through the circuit designated by numeral 22 and are passed through a heating coil 23 mounted in a furnace setting 24 through a circuit designated by numeral 25.

Tower I8 is maintained under a somewhat lower pressure than tower 5, say between 30 and 50 pounds per square inch, so that a pressure release valve IIa is provided in line I'I to effect the necessary reduction in pressure. tom of tower I8 is maintained at a temperature between say 400 and 450 F. by continuously circulating a portion of the bottoms withdrawn The bottherefrom through a heating coil. Thus a portion of the bottoms is withdrawn from tower I8 through line 26 by means of pump 21, forced through line 28 into and through a heating coil 29 which may be mounted in the same furnace setting 24 as heating coil 23 and then reintroduced into tower I8 through line 30 at a point near the bottom thereof. With the bottom of tower I8 maintained at a temperature of 400 to 450 F. in this manner, the top of tower I8 will be maintained at a temperature` between say 250 and 300 F.

A portion of the bottoms in tower I8 is withdrawn therefrom through line 3 I, passed through heat exchanger to give up part of its heat content to the bottoms'from tower 5, then passed through line 32 into a coolingmeans 33 and finally removed from the system through line 34. These bottoms will consist ofthe heavier fractions of the original naphtha feed.

The lighter fractions are removed from tower I8 through line 35, passed through a cooling means 36 and then discharged through line 31 into a, separator 38 from which uncondensed gases, if any, are withdrawn through line 39. Condensate is removed from separator 38 through line 40 by means of pump 4I and a small portion thereof is returned to the top of tower I8 through line 42 to act as reflux. The remainder-,of the condensate from separator 38 is forced through line 43 into a cooling means 45 and finally is removed from the system through line 45. This condensate `consists essentially of thev lighter, stabilized fractions of the original naphtha feed.

In the operation of the process it will be understood that the particular temperatures and pressures used will depend very largely upon the nature of the feed stock and the number and boiling range of the various fractions into which the feed is to be segregated.

The process of the invention is not restricted to a naphtha nor to the particular temperatures and pressures given above merely for illustrative purposes but is applicable in general to the treatment of any hydrocarbon distillate in which it is desired to remove a small amount of objectionable light ends and subsequently to separate the oil by frac,- tional distillation into various fractions of predetermined physical characteristics.

We claim:

1. An improved method fordesuliiding, stabilizing and fractionating a naphtha containing objectionable light ends which comprises introducing said naphtha into the top portion of a plate tower maintained under a superatmospheric pressure, maintaining the bottom portion of the tower at a temperature between 2'50 and 300 F.,

tower, withdrawing hot liquid from the bottom of `removing vapors ,and gases from the top of the change relationship to the liquid removed from vthe bottom of the first tower and nally coolmg -said condensate and the liquid from the second tower to form a lighter naphtha fraction and a heavier naphtha fraction.

2. An improved method for desulfiding, stabllizing and fractionating a naphtha containing objectionable light ends which comprises introducing said naphtha into the top portion of a plate tower maintained under a superatmospheric pressure, maintaining the bottom portion of the tower ata temperature between 250 and 300 F.,l

removing vapors and gases from the top of the tower, withdrawing hot liquid from the bottom of the tower, and introducing it without cooling and with the addition of further heat thereto into the middle portion of a second plate tower maintained under a lower superatmospheric pressure than the first tower, maintaining the bottom portion of the second tower at a temperature between 400 and 450 F., removing vapors from the top of the second tower and liquid from the bottom thereof, condensing a portion of the vapors so removed to form a condensate, passing the bottoms from the second tower in indirect heat exchange relationship to the liquid removed from the bottom of the first tower and nally'cooling said condensate and the liquid from the second tower to form a lighter naphtha fraction anda heavier naphtha fraction. Y

3. Improved method of separating a relatively small amount of normally gaseous materials from a relatively large amount of normally liquid hydrocarbon oil boiling in the range between naphthas and gas oils containing same, which consists in-introducing said oil as a liquid phase feed at a pressure not substantially above lbs/sq. in.

`as the sole feed into the top of a fractionating tower, heating said oil in the bottom of said tower to a temperature sufficient to vaporize the most volatile hydrocarbon constituents and to boil out hydrogen sulfide, removing the vaporized constituents from the top of the tower, withdrawing the hot bottoms from said tower and passing them into a second fractionating tower at a pressure substantially lower than the pressure in said first tower but not substantially above 50 lbs/sq. in., and subjecting said bottoms to frac'- tionation in said second tower, whereby the heat in said bottoms yfrom the first tower substantially assists the fractionation in the second tower.

4. Method according to claim 3 in which propane and lighter hydrocarbons are vaporized and removed from the first tower.

5. Improved method of separating a relatively small amount of Anormally gaseous materials from arelatively large amount of normally liquid naphtha containing same, which consists in introduring said naphtha as a liquid phase feed at a pressure of about 60-100 lbs/sq. in, as the sole feed into the top of a plate fractionating tower, heating said naphtha in the bottom of said tower to a temperature of about 250 to 300 F., thereby maintaining the top of the towerat a temper.- ature of 100 to 130 F., and thereby vaporizing tower while maintaining the bottom of said second tower at a temperature of 400 to 450 F. and the top of said tower at a temperature of about 250 to 300 F., whereby the heat in the naphtha 5 bottoms from the rst tower substantially assists the fractionation in the second tower` WALTER H. RUPP.

FRED C. HANKER, JR. 

